1. Field of the Invention
The present invention relates to a chemical solution vaporizing tank and a chemical solution processing system for producing a processing gas by supplying a vaporization gas (i.e., a gas for vaporization) to a stored chemical solution and supplying the processing gas to a work for processing it.
2. Description of the Background Art
In a photoresist step that is one of semiconductor manufacturing steps, a resist pattern is formed by applying resist over a surface of a semiconductor wafer that is a substrate (and will be referred to as a “wafer” hereinafter), exposing the resist with a predetermined pattern and then developing it. This processing is generally performed with a system in which an exposing device is connected to a coating and developing device performing the coating and development of the resist.
The coating and developing devices may be provided with various liquid processing devices that perform processing by supplying a chemical solution to substrates. For example, the liquid processing device is formed of a chemical solution vaporizing tank for vaporizing the processing chemical solution, and a processing module that forms a processing space accommodating a wafer and processes it by supplying the vaporized processing chemical solution. More specifically, as an example of the liquid processing device, there is a hydrophobic processing system that performs hydrophobic processing on a wafer before applying resist for the purpose of improving adhesion of the resist to the wafer. This hydrophobic processing system includes an HMDS solution vaporizing tank for vaporizing an HMDS (HexaMethylDiSilazane) solution, and a hydrophobic processing module performing the processing by supplying the HMDS gas to the wafer. The liquid level of the HMDS solution in the tank is managed to fall within a predetermined range, vaporization efficiency is controlled to fall within a predetermined range and an HMDS gas within a predetermined concentration range is supplied to the hydrophobic processing module. Usually, the coating and developing device is provided with the plurality of such hydrophobic processing modules for improving a throughput, and the chemical solution vaporizing tanks already described are individually arranged for the respective hydrophobic processing modules.
As a time elapses since the solution such as the HMDS was supplied into the chemical solution vaporizing tank, a degree of freshness of the solution decreases, and the concentration lowers due to decomposition so that the effect thereof on the wafer deteriorates. Therefore, when a difference occurs in condition of use of the HMDS between the tanks due to operating conditions of the respective processing modules, a difference occurs in freshness of the HMDS between the tanks, and thus occur in state of the hydrophobic processing between the wafers so that yield may lower. In the foregoing structure having the coating and developing device that includes the plurality of hydrophobic processing systems, the structure may employ the HMDS solution vaporizing tanks equal in number of the hydrophobic processing modules. This increases a space required for installing these hydrophobic processing systems, and thus disadvantageously increases the installation space of the developing device.
Japanese Utility Model Publication No. 7-34936 has disclosed a structure in which a chemical solution vaporizing tank is shared among a plurality of processing modules, and is partitioned into chambers between which a solution can flow, and vaporizing processing is performed by bubbling in each of the separated chambers. However, the respective chambers of the tank are connected to the processing modules by pipes, and difference in pressure loss in the pipe usually occur between the pipes due to differences in diameter and/or length between the pipes. Due to an influence of the pressure losses in the pipes as well as the foregoing differences in operation condition between the processing modules, differences in pressure between the separated chambers increase as the processing gas is supplied into the respective processing modules, and differences gradually occurs in chemical solution level between the chambers. Thereby, a ratio between the chemical solution and the gas varies in each chamber, and consequently the vaporization efficiency varies in each chamber independently of the other chambers so that differences occur between the concentrations of the HMDS gas supplied to the respective modules, resulting in a problem that the control becomes impossible.